This invention relates to magnetic components for use, for example, in power supply units.
Magnetic components such as transformers and inductors are typically expensive and bulky components due to the physical and electrical requirements of such components. They find general application in many areas of circuit design. One application of such devices is in power supplies.
Different constructional techniques are known for manufacturing such magnetic components. One known type of magnetic component is called a planar magnetic component. Planar magnetic components have spiral windings formed on different layers of a multilayer circuit board and ferrite cores are provided to couple the windings. Examples of planar transformers are described in U.S. Pat. Nos. 5,353,001 and 5,598,327. These transformers form discrete components for mounting on a circuit board to form part of a conventional circuit. Accordingly, although the planar transformers can be made relatively compact, the overall circuit is still bulky and expensive due to the need to mount discrete magnetic components on a circuit board to form the circuit of which the planar transformer forms a part. There is a need further to reduce costs and improve space utilisation for power supply circuits and the like.
U.S. Pat. No. 5,583,474 describes examples of magnetic components (transformers or inductors) for an integrated circuit, the magnetic components comprising spiral windings formed between and insulated from first and second magnetic layers. Such a planar magnetic component can be integrated with active (e.g transistor) and passive (e.g. resistor or capacitor) elements within the integrated circuit. Such magnetic components for integration in an integrated circuit are suitable for low current applications. Accordingly, they are not suitable for higher power applications such as power supplies, for example. Moreover, there is no teaching of how to provide plural magnetic components for a conventional, non-integrated circuit, for example for a power supply.
A particular application of the invention relates to providing an efficient power supply unit with high power density, for example a 5 volts 70 amp power supply. It is proposed to provide a soft-switching phase shift control conversion topology, with the addition of current doubler synchronous rectification at its output stage. For such a topology, it is proposed to use four magnetic components, namely, a transformer, a commutating choke in series with the primary winding of the transformer, and two output filter inductors in series with the secondary winding of the transformer. However, using prior art techniques, the need for four magnetic components would result in a bulky and expensive power supply unit. Accordingly, there is a specific need to reduce the size and cost of such a power supply unit.
However, it should be noted that the aforedescribed power supply is but one application for the instant invention as there is, more generally, a need to enable to provision of multiple magnetic components in a more compact and cost efficient manner.
Thus, an aim of the present invention is to improve the provision of multiple magnetic components.